With relatively superior physical, chemical and mechanical properties, high molecular weight polyethylene is often used for making artificial joint cups. However, as shown from clinical observations and experiment researches through many years, when matched with metal caput femoris, a high molecular weight polyethylene joint cup has relatively low hardness. In particular, after bearing a large load for long time, the high molecular weight polyethylene joint cup may generate wear-off particles, which may cause bone lysis on some surfaces of the bone joint, and then result in prostheses loosening and shortened service life of the artificial joint cup, thereby increasing clinical risks for a patient in receiving artificial joint revision surgery for second and third times.
In recent years, a matching mode of the same material, such as “ceramic-ceramic” or “gold-gold”, has been tried in artificial hip joint prosthesis so as to solve boundary wearing problems between different materials. However, clinical trials have shown that there are still defects in “ceramic-ceramic” or “gold-gold” matching. For example, “ceramic-ceramic” joints are fragile, which limits the activity level and range of the postoperative patients; “gold-gold” joints have significant requirements on surgery condition and physicians' surgery skills; and a slight deviation in a joint replacement may accelerate wearing at joint edges and then generate large quantities of chippings and abnormal noises. Therefore, for artificial hip joints, the majority products still use the matching mode of a high molecular weight polyethylene joint cup and metal ball.
High molecular weight polyethylene wearing is mainly affected by material performance and the processing procedure. Researches have used crosslinking modification and physical modification to improve wear resistance of high molecular weight polyethylene. For regarding radiation crosslinking modification, there are oxidation and catalysis problems for high molecular weight polyethylene; for ion injection crosslinking modification, limited ion injection depth (at 50˜100 keV injection energy, layer thickness is about 0.1˜0.2 μm) cannot meet requirements on a medical high molecular weight polyethylene material; the physical filling mode improves the wear resistance, but it reduces the tensile strength, shock-absorbing strength, elongation at break and other important mechanical properties. Therefore, the above mode is mainly applied to industrial fields at present.
Through a coating technology, additional properties may be added to a substrate material. Researches have tried to coat a diamond-like carbon film over a surface of high molecular weight polyethylene joint cups to improve the wear resistance of a high molecular weight polyethylene material while guaranteeing the properties of the high molecular weight polyethylene material at the same time. However, as a soft material, high molecular weight polyethylene has poor heat resisting property, and is readily to be carbonizable and oxidizable; therefore, to deposit a coating on the material, there are high requirements on the coating processes and equipment. As how to realize coating on a high molecular weight polyethylene surface under nondestructive conditions, there are extremely high requirements on the design of coating material system, process requirement and equipment performance. At present, there is still no similar product in the market.
The applicant's prior invention with the publication number of 201210151152.2 has disclosed a magnetron sputtering coating device, a nano-scale multilayer film and a manufacturing method thereof. In that application, a special sputtering device and sputtering technology are adopted to perform a technology of coating a carbon film in a nano-scale multilayer structure on an artificial joint or the like with high molecular weight polyethylene as a matrix. The matrix comprises a TiC and graphite-like transition layer, a multilayer structure with alternative laminating of graphite-like layers and diamond-like carbon layers, and a top film structure of diamond-like carbon. Based on the material system, the technical solution has considered poor heat resisting property, readily carbonizable and oxidizable properties, readily dissociative and crosslinking properties of the main chain or the side chain of high molecular weight polyethylene, and intends to construct a new material system and a manufacturing method thereof on a high molecular weight polyethylene joint cup surface to solve a poor binding force problem between the film and the matrix, while solving the easy oxidization and carbonization problems of high molecular weight polyethylene with a low temperature magnetron sputtering technology.
Through research and practice, the applicant has improved the shortcomings of the technical solution as discussed above, and has developed improvement plans regarding the device and method for manufacturing the product.